Dynamically generated MacroPlaceholder in Editor (Server)

Hello everyone,

i am trying to generate / change the macro placeholder dynamically after the user entered some value in the edit page.
It should work exactly like e.g. the status macro (example below).
I already managed to expand the property panel of the macro so that the user can enter a value.
What i now want to do is to create an image (if needed?) depending on the user input and replace the macro placeholder with that image instantly.

The tutorial (https://developer.atlassian.com/server/confluence/providing-an-image-as-a-macro-placeholder-in-the-editor/) only shows how some predefined pictures can be displayed.
But i need to create the image depending on the user input.

The behaviour should be like in this Status macro:

Either generate the image and insert it into a DownloadableResource, then return the URL to that resource, or return the URL to a service that generate/return the image.